A conventional router typically includes a set of Ethernet ports and a serial console port. Each Ethernet port typically includes an RJ-45 style female jack to receive a connecting end of an Ethernet cable (e.g., a Cat-3, Cat-5, Cat-5e or better). The serial console port typically includes a DB-9 or DB-25 connector or an RJ-45 jack to receive a connecting end of an RS-232 cable.
During operation, the conventional router sends and receives Ethernet communications signals through its Ethernet ports. Each Ethernet communications signal is a differential signal having a positive (+) signal component and a negative (−) signal component which is opposite the positive signal component and isolated from ground. Some router devices operate as PSE (power sourcing equipment) to provide power concurrently with communications signals through the Ethernet ports to PDs (powered devices) in accordance with established Power over Ethernet (PoE) standards.
In contrast to the above-described Ethernet ports which carry Ethernet communications signals and possibly power, the serial console port provides an administrative interface for a local “dumb” terminal. That is, the serial console port is a serial communication physical interface through which a user is able to carry out a number of local administrative functions that could not or should not be conducted over an Ethernet connection. For instance, the operating system of the router may treat a user login session through the local terminal, which is connected to the serial console port, as more trustworthy/secure.